By:       Norm Goyer

The Bell P-39 Airacobra was the most unusual and controversial yet successful fighter of World War II. It was manufactured as a result of a proposed purchase order for a fighter aircraft, different than any other ever manufactured. The specifications had two very unusual requisites, the engine was to be installed in the middle of the aircraft, behind the pilot, driving a ten foot drive shaft in a tunnel under the cockpit floor. This was required because an Oldsmobile produced cannon was to be installed behind the propeller shooting through its hollow propeller shaft. The specs also called for an external turbo supercharger to allow the Allison V-12 engine to attain higher altitudes. This last request became the single largest problem of the Airacobra. The unusual engine position caused CG balance problems with the possibility of a flat spin. There never was a problem with the drive shaft, which turned out to be almost maintenance free. The engineers had placed a junction in the shaft allowing it to  self center when the fuselage was twisted due to aerodynamic loads. Production models were shipped with only a single stage supercharger. The aircraft had very poor high altitude ability.

This Bell P-39-Q has been restored and is often seen at major air shows.

Aviation history books have this to say about the Oldsmobile cannon: “The main purpose of this configuration (engine behind the pilot) was to free up space for the heavy main armament, a 37 mm (1.46 in) Oldsmobile T9 cannon firing through the center of the propeller hub for optimum accuracy and stability when firing. In fact, the entire design was made to accommodate this gun in the aircraft. This happened because H.M. Poyer, designer for project leader Robert Woods, was impressed by the power of this weapon and pressed for its incorporation though the original concept had been a 20–25 mm (.79–98 in) cannon mounted in a conventional manner in the nose. This was unusual, because fighters had previously been designed around an engine, not a weapon system. Although devastating when it worked, the T9 had very limited ammunition, a low rate of fire, and was prone to jamming.”

The P-39 was very effective as a low-level fighter due to its cannon and mid engine.

This cannon was the main reason that Russian pilots flying P-39s had such a success using the P-39 against ground troops, air to air and as an airborne tank buster. A Russian pilot managed to confirm 54 kills in his Airacobra against German aircraft, including Bf.109s, FW.190s. In fact, this Russian Pilot pushed the Airacobra into the record books as being the only American built aircraft to achieve such a high kill rate. There were almost 10,000 Airacobras built and Russian had almost half of them.

The P-39 Airacobra was very fast but lacked high altitude performance.

The Airacobra was flying with Army Air Force units in 1939. After Pearl Harbor, the P-39 was deployed to training units, but some did see combat in the Southwest Pacific with the Cactus Air Force in the Battle of Guadalcanal. Though outclassed by Japanese fighter planes, it performed well in strafing and bombing runs, often proving deadly in ground attacks on Japanese forces trying to retake Henderson Field. Guns salvaged from P-39s were sometimes fitted to Navy PT boats to increase firepower.

The Allison V-12 engine, located behind the pilot, had a 10 foot two-section drive shaft running in a tunnel beneath the floorboards. This never presented a problem.

England reassigned their lend lease P-39s to Russia as the plane had the same problems as early P-51s did; they were unable to climb and fight at the altitudes needed. The single stage supercharger ran out of steam above 12,000 feet. Air to air combat often occurred way above that altitude. The P-51 was refitted with a Rolls Royce turbo supercharged engine which solved the problem, the Airacobra could not, due to the unusual location of the engine and lack of room.

The Airacobra was deployed to Alaska where poor weather caused a large number of crashes.

The Airacobra also had a very difficult time while deployed to Alaska and the Aleutian Islands. From September to November 1942, pilots of the 57th Fighter Squadron flew P-39s and P-38s from an airfield built on land bulldozed into Kuluk Bay on the barren island of Adak in Alaska’s Aleutian Islands. They attacked the Japanese forces which had invaded Attu and Kiska islands in the Aleutians in June 1942. The number one foe that claimed the most lives, however, was not the Japanese but the weather. The low clouds, heavy mist and fog, driving rain, snow and high winds made flying dangerous and lives miserable. The 57th remained in Alaska until November 1942 and then returned to the United States.

Aviation history has to be kind to the Airacobra in spite of its many problems. It wasn’t the perfect fighter aircraft but when flown by competent pilots it performed unlike any other. It became the perfect backup fighter. Many times countries needed fighter aircraft and the only available one was the P-39. Towards the end of World War II Bell introduced the Bell P-63 King Cobra. Bell had managed to solve some of the problems but it was too late, the war was winding down.

General characteristics P-39Q

• Crew: One

• Length: 30 ft 2 in

• Wingspan: 34 ft

• Height: 12 ft 5 in

• Wing area: 213 sq ft

• Empty weight: 5,347 lb

• Loaded weight: 7,379 lb

• Max takeoff weight: 8,400 lb

• Powerplant: 1, Allison V-1710-85 liquid-cooled V-12, 1,200 hp

• Performance

• Maximum speed: 376 mph  (Redline dive speed was 525 mph)

• Range: 525 miles on internal fuel

• Service ceiling: 35,000 ft

• Rate of climb: 3,750 ft/min

• Wing loading: 34.6 lb/sq ft

• Power/mass: 0.16 hp/lb

• Time to climb: 15,000 in 4.5 min at 160 mph

Armament

• Guns:

  • 1, 37 mm M4 cannon with 30 rounds of HE ammo.

  • 2, .50 cal (12.7 mm) machine guns. 200 rounds per nose-gun

  • 4, 30 cal machine guns, wing mounted. 300 per wing-pod

• Bombs: Up to 500 lb of bombs externally

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